The present invention relates to a packet relay device and, in particular, a high-reliability technology that is intended to enhance communication reliability using a redundant configuration and a packet relay device that reduces excess power.
The number of packet relay devices, which are routers or switches, has increased. High-volume information such as moving images has widely been used. As a result, intra-network traffic volumes have rapidly increased. Moreover, the power consumption of packet relay devices in Japan in 2025 is estimated to be 13 times more than that in 2006. Saving power in packet relay devices is an important challenge that helps prevent global warming.
To achieve the above, JP-A-2007-228491 discloses a technology that changes the clock frequency of a packet transfer unit which determines the transfer destination of received packets. “AX6700S/AX6300S Software Manual Configuration Settings, Vol. 1 Ver. 10.3 compatible, ALAXALA Networks Corporation, November 2006, pp. 181 to 182” describes a technology that restrains the power supply to ports connected to network lines as well as the power supply to packet transfer units.
On the other hand, simply saving power in a packet relay device sacrifices the continuity of communication. For this reason, power-saving technology is often used in combination with reliability technology that makes ports or packet transfer units redundant. Examples of technology that makes ports redundant include link aggregation, which is standardized as IEEE802.3ad. Link aggregation is a technology that, by handling multiple ports as a single line logically, expands the band as well as allows communication to continue even when a single line fails. To avoid communication interruption in link aggregation, JA-A-2008-098720 discloses a method of dynamically changing the number of ports included in link aggregation in accordance with the time zone or the traffic volume. JA-A-2008-244907 discloses a method of always synchronizing control information about link aggregation among multiple network interfaces.
Technologies that make packet transfer units redundant include a technology that uses all the redundant packet transfer units as active packet transfer units and a technology that places some of the redundant packet transfer units on standby as backups to be used when a failure occurs. Technologies that place some packet transfer units on standby include “hot standby,” which keeps the standby packet transfer units in the same state as that of the active packet transfer units and can immediately replace a failed active packet transfer unit with a standby network interface, and “cold standby,” which takes some time for such replacement. Generally, cold standby is more advantageous in terms of the amount of power reduction.